The present invention relates generally to a silicone room temperature vulcanizing (RTV) elastomer layer which adheres a film to a condensing heat exchanger without utilizing a primer and adhesive.
Condensing heat exchangers are employed in condensing furnaces to increase efficiency. The condensing heat exchanger cools the heating fluid to a temperature below the dew point. As the temperature drops below the dew point, a liquid condensate, water vapor, condenses from the heating fluid. As the liquid condensate condenses, heat is transferred from the water vapor to the air to be heated. As more heat is produced, the efficiency of the system is increased.
Polypropylene films are commonly utilized to make a laminate for a condensing furnace heat exchanger to prevent corrosion by the water vapor liquid condensate. The present method of making the laminate is expensive. A primer is first applied to the pretreated steel of the condensing heat exchanger. After a bake cycle, an adhesive is applied, following again by a bake cycle. The polypropylene film is then thermally laminated to the adhesive, attaching the film to the metal surface of the condensing heat exchanger.
There are several drawbacks to utilizing the primer and adhesive of the prior art. For one, both the primer and the adhesive contain high percentages of expensive solvents which must be combusted to meet xe2x80x9cclean airxe2x80x9d regulations. Additionally, the formulation of the primer is occasionally changed by the manufacturer, resulting in production problems and failed inspections.
Hence, there is a need in the art for a layer which adheres a film to a condensing heat exchanger without utilizing a primer and adhesive.
The present invention relates to a silicone RTV elastomer layer which adheres a film to a condensing heat exchanger without utilizing a primer and adhesive.
A film is adhered to a metal plate of a condensing heat exchanger by a cured silicone RTV elastomer to prevent corrosion of the condensing heat exchanger. The surface of the metal plate is pretreated by a layer of phosphate or chrome. A layer of solid silicon RTV elastomer including an organosilicone functional group which cross-links with the aid of water is then applied on the pretreated metal surface. Preferably, the layer of silicone RTV elastomer is applied by a roller. The silicone RTV elastomer layer is preferably applied between 0.1 and 10 mils in thickness.
After the layer of silicone RTV elastomer is applied to the surface of the condensing heat exchanger, the metal plate is heated and a protective film is applied. The film is adhered to the surface of the metal sheet by curing the layer of silicone RTV elastomer with water a room temperature. Water cross-links the organosilicone functional groups on the silicone RTV elastomer to create an adhesive surface which adheres the film to the surface.
Accordingly, the present invention provides a silicone RTV elastomer layer which adheres a film to a condensing heat exchanger without utilizing a primer and adhesive.